You undoubtedly already know that sleeping with your neck entirely bent forward might result in headaches, or that a bad mattress can cause back discomfort. But did you know that your sleeping position can have other effects on your health, and even increase or decrease your risk of certain diseases? Here are five health issues that research suggests may be brought on, made worse by, or helped by various sleeping positions, though the strength of the evidence varies.
You likely know people who snore loudly, almost gagging periodically during the night as their breathing ceases and then resumes. This condition is known as obstructive sleep apnea and is linked to a host of health problems. An Israeli study in the Journal of Clinical Sleep Medicine looked at how sleeping position may affect sleep apnea and found that the subjects who slept on their back experienced more frequent apnea, as well as hypopneas (periods of abnormally low or shallow breathing).Sleeping on your back can worsen not just obstructive sleep apnea but also other sleep-related breathing disorders.
What it is about lying on your back that makes apnea worse compared with lying on your side? Research suggests it’s because when you’re on your back, gravity causes the soft palate and base of the tongue to slacken and collapse into the rear of the throat, which can make breathing difficult in some people.
Acid reflux (GERD)
If you suffer from acid reflux, you may know what sets it off: perhaps a heavy, late-night meal or a couple of cocktails before hitting the sack. But there’s also evidence that sleeping on your right side is linked with greater reflux symptoms. One possible reason experts have proposed is that sleeping on the right side encourages relaxation of the sphincter (muscle ring) at the base of the esophagus that keeps stomach acid from backing up into the delicate tissues of the esophagus, though this hasn’t been proved. In contrast, when you lie on your left side (the side where the stomach is located), part of the stomach rests lower than the esophagus, so acids have more trouble migrating up. (Also, the sphincter pressure may be higher in that position.) An older paper in the American Journal of Gastroenterology found that subjects who ate a fatty dinner and bedtime snack and then slept on their right side experienced greater acid levels that those who slept on their back, stomach, or left side. And the acid took a longer time to clear from the esophagus in the right-side sleepers.
In addition to sleeping on your left side, elevating the head of your bed or using a special, wedge-shaped pillow or blocks under the legs of the head of the bed to elevate your upper body may also help ease acid reflux.
Many things can cause you to wake up in the night (or first thing in the morning) with neck pain, but your sleeping position should be one of the first factors you consider. While experts don’t agree about what the best sleeping position is for preventing neck discomfort, there is some consensus that sleeping on your stomach should be avoided. Typically, when you lie face down, your head twists one way or the other, putting stress on the neck or cervical vertebrae. A small study in The Internet Journal of Allied Health Sciences and Practice,in which participants were interviewed by phone about their sleep habits and physical symptoms, found that subjects who slept mostly on their side were less likely to report waking with neck, arm, or shoulder pain.
The pillow you choose can also play a role. In another very small study, conducted in Taiwan, investigators used an infrared video camera to watch sleeping subjects. They found that the neck awkwardly bent forward when the subjects slept on their back, perhaps because the pillow was too thick (and thus their head positioned too high). Yet when they turned onto their side, that same pillow was too narrow to keep their head aligned with their spine, which also caused an unnatural bending in the neck. So the trick may be to experiment with pillow sizes and thicknesses to find what works best with your sleeping position.
The cause of most nightmares is largely a mystery. They have been linked to a host of factors, from certain prescription drugs to psychological stress, but sleeping position may also play a role in some of them. In a study published in Sleep and Hypnosis over a decade ago, participants reported on their sleeping position, dreams or nightmares, and sleep quality. Those who usually slept on their left side reported significantly more frequent nightmares than those who slept on their right side, who tended to report more positive dreams and better quality sleep.
Even though it probably sounds absurd, there is some very preliminary evidence from animal studies that suggests sleeping on your side may help lower your risk of developing several neurological diseases, such as Parkinson’s and Alzheimer’s. In a recent study published in the Journal of Neuroscience, scientists conducted medical imaging scans on anesthetized rodents that were placed in three different sleep positions: back, stomach, or side. The investigators were interested in the brain’s waste clearance system, known as the glymphatic pathway, which may play a role in Alzheimer’s and other neurological conditions. The animals’ glymphatic pathways appeared to work more efficiently when they slept on their sides. Of course, a great deal more research would be needed to determine whether side sleeping actually affects this neurological pathway—or the associated risk of Alzheimer’s and other diseases—in humans.